I'd probably email the guy and copy/paste your details on it as was sent on the invoice and ask where it stated that it was to be delivered to Sydney?? I would also double check where they would ship to etc as well incase they only listed local shipping (which doesn't seem likely but best to cover all bases) and then put it to him...ask how it becomes your fault for a incorrect address when the address was clearly sent to them in the ebay invoice system.

failing that, you can actually write a dispute to ebay and both can have the feedback withdrawn.